Transfer Matrix Model Research Articles

Pogo Stability Approaches for the Strap-On Launch Vehicle with Staged Combustion Cycle Engines

According to the new characteristics of the solid–liquid strap-on launch vehicle and the liquid oxygen/kerosene staged combustion cycle engines, a finite element model of the launch vehicle propulsion–structure coupled system subjected to pogo was presented in this paper. In the model, the structure was represented by a longitudinal–lateral–torsional integrated finite element model with a three-dimensional tank and one-dimensional beam–spring–mass. The propulsion system was represented by a transfer matrix model, which was fitted by the vector fitting method and transformed into a second-order differential equation. By assembling the structure dynamic equations and propulsion system, the governing equation of the coupled system can be established. After that, pogo stability was analyzed by solving the complex eigenvalues of the governing equations. The method developed in this paper can also be expanded to other liquid launch vehicles.

Determination of the modal parameters of a single lap adhesively bonded joint using the transfer matrix method plus model updating

An approach that combines the transfer matrix method (TMM) and single variable model updating is proposed to determine the natural frequencies and mode shapes of a cantilever beam formed by an adhesively bonded single lap joint (SLJ). When the TMM is applied to the SLJ beam, the key is to determine the effective density and effective elastic modulus for the overlap region element. In this study, the effective density is determined using a volume fraction approach and the effective elastic modulus is determined using a single variable model updating approach. This approach is compared with a commonly used additive approach to determine the overlap region effective elastic modulus. The performance of the proposed single variable model updating approach is evaluated using a finite element model and experimental testing as benchmarks. The proposed single variable TMM model updating approach consistently outperforms the additive approach for the single lap joint specimens considered. Further, the robustness and general applicability of the overlap region effective elastic modulus are demonstrated, including its ability to deal with uncertainty. Insights about the impact of selected structural modifications on the natural frequencies of the single lap joint specimens are discussed.

Solution-processed antireflective coating for back-contact perovskite solar cells.

Back-contact architectures for perovskite solar cells eliminate parasitic-absorption losses caused by the electrode and charge collection layers but increase surface reflection due to the high refractive index mismatch at the air/perovskite interface. To mitigate this, a ∼85 nm thick layer of poly(methyl methacrylate) (PMMA), with a refractive index between those of air and perovskite, has been applied as an antireflective coating. Transfer matrix modelling is used to determine the ideal PMMA layer thickness, with UV-Vis spectroscopy measurements used to confirm the increase in absorption that arises through the application of the antireflective coating. The deposition of a thin film of PMMA via spin coating onto a solar cell results in a 20-30% relative increase in short circuit current density and stable power output density.

Beyond Ti3C2Tx: MXenes for Electromagnetic Interference Shielding.

New ultrathin and multifunctional electromagnetic interference (EMI) shielding materials are required for protecting electronics against electromagnetic pollution in the fifth-generation networks and Internet of Things era. Micrometer-thin Ti3C2Tx MXene films have shown the best EMI shielding performance among synthetic materials so far. Yet, the effects of elemental composition, layer structure, and transition-metal arrangement on EMI shielding properties of MXenes have not been explored, despite the fact that more than 30 different MXenes have been reported, and many more are possible. Here, we report on a systematic study of EMI shielding properties of 16 different MXenes, which cover single-metal MXenes, ordered double-metal carbide MXenes, and random solid solution MXenes of M and X elements. This is the largest set of MXene compositions ever reported in a comparative study. Films with thicknesses ranging from nanometers to micrometers were produced by spin-casting, spray-coating, and vacuum-assisted filtration. All MXenes achieved effective EMI shielding (>20 dB) in micrometer-thick films. The EMI shielding effectiveness of sprayed Ti3C2Tx film with a thickness of only ∼40 nm reaches 21 dB. Adjustable EMI shielding properties were achieved in solid solution MXenes with different ratios of elements. A transfer matrix model was shown to fit EMI shielding data for highly conductive MXenes but could not describe the behavior of materials with low conductivity. This work shows that many members of the large MXene family can be used for EMI shielding, contributing to designing ultrathin, flexible, and multifunctional EMI shielding films benefiting from specific characteristics of individual MXenes.

Torsional vibration analysis of a planetary gear type antiresonant vibration isolator using transfer matrix method, Part I: System modeling

Recently, a new type of vibration isolator called a dynamic antiresonant vibration isolator (DAVI) has been studied for torsional systems as well as translational systems. In the DAVI for torsional systems, the inertia coupling for the anti-resonance effect is generated by a planetary gear that connects control inertia and inertias at the input and output terminals. In this research, an analytical modeling approach called the transfer matrix method is applied to design a planetary gear type DAVI for complex systems such as an automotive powertrain. Unlike a previous study, inertias of the pinion gears are newly included in the transfer matrix model to improve the model accuracy in this paper. In this part 1 of series papers, the internal configuration of a planetary gear type DAVI system is described and its dynamic model is derived using the transfer matrix method. The derived transfer matrix model is then validated by comparing its frequency response with those obtained by conventional and numerical methods. Finally, the effects of different gear ratios and pinion gear inertia are examined using the derived transfer matrix model.

Impacts of Precipitation and Temperature on Changes in the Terrestrial Ecosystem Pattern in the Yangtze River Economic Belt, China.

The terrestrial ecosystem plays an important role in maintaining an ecological balance, protecting the ecological environment, and promoting the sustainable development of human beings. The impacts of precipitation, temperature, and other natural factors on terrestrial ecosystem pattern change (TEPC) are the basis for promoting the healthy development of the terrestrial ecosystem. This paper took the Yangtze River Economic Belt (YREB) as the study area, analyzed the temporal and spatial characteristics of TEPC from 1995 to 2015, and used spatial transfer matrix and terrestrial ecosystem pattern dynamic degree models to analyze the area transformation between different terrestrial ecosystem types. A bivariate spatial autocorrelation model and a panel data regression model were used to study the impacts of precipitation and temperature on TEPC. The results show that: (1) The basic pattern of the terrestrial ecosystem developed in a relatively stable manner from 1995 to 2005 in the YREB, and transformations between the farmland ecosystem, forest ecosystem, and grassland ecosystem were more frequent. The temporal and spatial evolution of precipitation and temperature in the YREB showed significant regional differences. (2) There was a significant negative bivariate global spatial autocorrelation effect of precipitation and temperature on the area change of the forest ecosystem, and a positive effect on the area change of the settlement ecosystem. The local spatial correlation between precipitation or temperature and the terrestrial ecosystem showed significant scattered distribution characteristics. (3) The impacts of precipitation and temperature on TEPC showed significant regional characteristics on the provincial scale. The impact utility in the tail region is basically negative, while both positive and negative effects exist in the central and head regions of the YREB. Moreover, the impact showed significant spatial heterogeneity on the city scale. (4) The Chinese government has promulgated policies and measures for strategic planning, ecological environment protection, and economic support, which could effectively promote ecological and sustainable development of the YREB and promote the coordinated development of the ecology, economy, and society in China.

Modeling and implementation of tandem polymer solar cells using wide‐bandgap front cells

AbstractTandem device architectures offer a route to greatly increase the maximum possible power conversion efficiencies (PCEs) of polymer solar cells, however, the complexity of tandem cell device fabrication (such as selecting bandgaps of the front and back cells, current matching, thickness, and recombination layer optimization) often result in lower PCEs than are observed in single‐junction devices. In this study, we analyze the influence of front cell and back cell bandgaps and use transfer matrix modeling to rationally design and optimize effective tandem solar cell structures before actual device fabrication. Our approach allows us to estimate tandem device parameters based on known absorption coefficients and open‐circuit voltages of different active layer materials and design devices without wasting valuable time and materials. Using this approach, we have investigated a series of wide bandgap, high voltage photovoltaic polymers as front cells in tandem devices with PTB7‐Th as a back cell. In this way, we have been able to demonstrate tandem devices with PCE of up to 12.8% with minimal consumption of valuable photoactive materials in tandem device optimization. This value represents one of the highest PCE values to date for fullerene‐based tandem solar cells.

A Transfer Matrix Model of the IEC 60318-4 Ear Simulator: Application to the Simulation of Earplug Insertion Loss

The IEC 60318-4 ear simulator is used to measure the insertion loss (IL) of earplugs in the ear canal of an acoustical test fixture (ATF) and is designed to represent an average acoustic impedance (in a reference plane) of the human ear. The ear simulator is usually modeled using a lumped parameter model (LPM) which has frequency limitations and inadequately accounts for the thermo-viscous effects in the simulator. The simulator numerical models that can better deal with the thermo-viscous phenomena often lack essential geometric details. Most related studies also suffer from the lack of experimental validation of the models. Therefore, a transfer matrix (TM) model of the IEC 60318-4 simulator is proposed based on a direct assessment of its geometric dimensions. Such a model is of particular interest for designing artificial ear simulators. The variability in the simulator impedance due to the geometric uncertainties is quantified using the Monte Carlo method. The TM model is validated using i) a finite element (FE) model of the simulator and ii) impedance measurements with a sound intensity probe. It is found to better describe the simulator impedance above 3 kHz compared to the LPM. The TM model is then coupled to a FE model of an occluded ATF ear canal to simulate the IL of an earplug in the frequency range [100 Hz, 10 kHz]. In the model, the simulator is considered as a cylindrical cavity terminated by an equivalent tympanic impedance which is determined from the TM model to simulate the sound pressure measured at the real microphone position (not at the reference plane) in the ATF ear canal. The simulated IL is validated against i) that obtained with a complete FE model of the corresponding system and ii) measurements using an ATF. The TM model is shown to better agree with the simulator FE model than the LPM above 6 kHz regarding the earplug IL simulated using this method.

Circuit reliability prediction based on deep autoencoder network

As semiconductor feature size continues to decrease and the density of integration continues to increase, highly reliable circuit design is experiencing many challenges, including reliability evaluation, which is one of the most important steps in circuit design. However, faced with the very large scale of integrated circuits at present, traditional simulation-based methods are slightly inadequate in terms of computational complexity and do not apply to the circuits at the concept stage. To solve this problem, this paper presents a new prediction method for circuit reliability based on deep auto encoder networks. Firstly, we analyze and extract the main features associated with circuit reliability. Next, we construct an efficient method for data collection by combining the characteristics of the feature set with the requirements of deep auto encoder networks. Then, we build a deep auto encoder network model oriented to circuit reliability prediction in a supervised learning manner. Simulation results on 74-series circuits and ISCAS85 benchmark circuits show that although the accuracy of the proposed method is slightly lower than that of both the Monte Carlo (MC) method and the fast probabilistic transfer matrix (F-PTM) model, its time-space consumption is approximately constant on different circuits, and it is 102,458,469 times faster than the MC method, and approximately 4,383 times faster than the F-PTM model. Furthermore, the proposed method could be used to predict circuit reliability at the conceptual stage, and it is a very efficient approximation method that could greatly reduce the power consumption of the calculation.

Bayesian decay time estimation in a reverberation chamber for absorption measurements.

This work investigates the use of the initial decay time to obtain the Sabine absorption coefficient from measurements conducted in a reverberation chamber. Due to non-uniform distribution of sound absorption in the test chamber, measured energy decay functions exhibit multiple slopes, which cannot be evaluated unambiguously using linear regression as prescribed in the current standard (ISO 354, International Organization for Standardization, Geneva, Switzerland, 2003). As an alternative, this study proposes a Bayesian framework that allows estimating multiple decay parameters, hence capturing more accurately the energy decay features. Measurements are carried out in a reverberation chamber with and without diffusing elements to investigate the influence of diffusers on the absorption coefficient and on the decay process. Measured absorption coefficients of a porous sample are compared to theoretical values estimated with a transfer matrix model. The results show that the Sabine absorption coefficient calculated using the shortest decay time agrees well with the size-corrected theoretical absorption coefficient.

Fabrication and Characterization of 3D Printed Thin Plates for Acoustic Metamaterials Applications

This paper presents a 3D printing technique based on stereolithography and direct light processing for the fabrication of low resonance frequency thin plates suitable for acoustic metamaterials applications. It was possible to achieve a better resolution with respect to other 3D printing methods such as fusion deposition modeling and to obtain plates with a thickness of $70~\mu \text{m}$ . The plates were characterized using three different methods: laser Doppler vibrometer supported by modal analysis, impedance tube measurements backed by a transfer matrix model and nanoindentation. All results are in good agreement. The physical parameters retrieved through the characterization methods can be used for future designs and integrated into finite element analysis to better predict the noise impact of these materials. Thanks to the small radius and thickness of the plates presented in this paper and to their low resonance frequency, it is suggested that they could be arranged in various configurations and used as unit cells in acoustic metamaterials applications for noise attenuation in small-scale electroacoustic devices.

Evanescent and propagating electromagnetic waves in Bi-isotropic layers

This paper presents a theoretical study of evanescent and propagating electromagnetic waves in bi-isotropic layers. The dispersion relation, guided mode condition, and evanescent wave coupling and tunneling in a bi-isotropic slab placed in a contrast bi-isotropic ambient medium are derived. A transfer matrix model is developed to acquire the transmission and reflection coefficients across the bi-isotropic layers. The creation of discrete guided modes and the continuous interval where the discrete guided modes are conceived are determined. Additionally, the effects of the Tellegen and chirality parameters on the width of the continuous interval are explained. The field distribution reformed by evanescent wave coupling and tunneling through the bi-isotropic slab is presented. The contrast bi-isotropic structure displays an evident high-pass frequency response that is controlled by the chirality of the slab. The behavior of the transmittance response with the material parameters and the incidence angle can facilitate the possible design of future electromagnetic and optical devices.

Perovskite solar cell towards lower toxicity: a theoretical study of physical lead reduction strategy

The huge performance enhancements of the organometal halide perovskite solar cells (OHPSCs) have appealed enormous attention within recent ten years. Although the rapid growth of the device power conversion efficiency (PCE) has attained over 25%, the contamination of health-hazardous components still holds back its sustainable applications. To reduce the lead usage, many groups have tried chemical lead reduction solutions: substituting the lead by other group 14 metal elements to realize the low-lead OHPSCs. Unfortunately, neither the PCE nor the stability, low-lead OHPSCs all lag far behind the state-of-the-art conventional lead-based OHPSCs. In this work, we present a physical lead reduction (PLR) concept by reducing the perovskite film thickness to restrict the perovskite hazard risk with minor scarification in device performances. Through the simulation of transfer matrix model, we theoretically demonstrated that by introducing the optical space layer, the device PCE could maintain 96% of the original maximum value while attenuating the perovskite film thickness to one-third. This means that the usage of lead can be reduced by ∼70% with PLR concept, which could have broad appeal as a new lead reduction strategy towards high performance OHPSCs.

Dispersion of Third‐Harmonic Generation in Organic Cavity Polaritons

AbstractOrganic cavity polaritons are bosonic quasiparticles arising from the strong interaction between organic molecular excitons and photons within microcavities. The spectral dispersion of third‐harmonic generation near resonance with cavity polaritons is studied experimentally via angle‐resolved reflected third‐harmonic generation measurements with several pump wavelengths. Moreover, a three‐step nonlinear optical transfer matrix model is used to simulate the third‐harmonic generation using the sum‐over‐states dispersive nonlinear coefficients, which include polariton states. The angle‐dependent experiment and modeling agree, revealing the output of third‐harmonic generation is resonantly enhanced when third‐harmonic wavelengths are near upper polaritons. Lower‐polariton‐enhanced third‐harmonic generation is not experimentally observed due to inadequate coupling at the longer wavelength, which is also consistent with the nonlinear transfer matrix modeling. These results indicate that the sum‐over‐states nonlinear dispersion is descriptive of the nonlinear optical process so that the polariton states belong to a complete set of states for a perturbative determination of the nonlinear optical response. From these results, it might be expected that such a basis for perturbation theory would be widely applicable for nonlinear optical processes in the strong and ultrastrong limits. The results also indicate the possibility of wavelength agile nonlinear optical response by angle‐of‐incidence tuning.

Demagnetization field driven charge transport in a TiO2 based dye sensitized solar cell

We report on the effect of demagnetizing fields due to magnetite (Fe3O4) nanoparticles (NPs) on the efficiency of TiO2 based dye sensitized solar cells (DSSC). The addition of Fe3O4 NPs into the photoanode enhanced the power conversion efficiency of DSSC. This may be attributed to the magnetic field effect induced by the demagnetizing field produced by the magnetite NPs, which is evident from our micromagnetic simulation. Essentially, such a stray field would induce additional force on the electron motion and thereby enhancing the recombination time of these charge carriers. Enhancement in recombination time is directly evidenced by the increase in short circuit current density. In addition, we have carried out an electrochemical impedance spectroscopy (EIS) study to probe the mechanism of charge transport within the DSSC device. Quenching of intensity in phosphorescence data indeed infer a decrease in recombination rate. We calculated the value of demagnetization energy from NPs with micromagnetic simulations. Absorbed energy density of ‘s’ and ‘p’ polarized incident light estimated using transfer matrix model.

Photonic Band Gap Properties of One-dimensional Generalized Fibonacci Photonic Quasicrystal Containing Superconductor Material

In this work, we theoretically investigate the transmission properties of one-dimensional (1D) Fibonacci photonic quasicrystal (PQC) by using the transfer matrix modeling (TMM) method. The PQC structure is composed of alternated layers of isotropic dielectric (SiO2) and a high-Tc superconductor (YBCO). Frequency-dependent dispersion formula according to the two-fluid Gorter–Casimir theory has been adopted to describe the optical response of the superconducting material. Within the framework of the TMM method, we studied the effect of many parameters such as the thicknesses of the dielectric and superconductor layers, Fibonacci lattice parameters, and the operating temperature on the transmission behaviors of the PQC structure. Our numerical results reveal the transmission cutoff frequency can be tuned efficiently by the operating temperature as well as by the thicknesses of the constituent materials. We found that increasing the temperature and the angle of incidence, maintaining materials thicknesses constant, there is a shift of the cutoff frequency to lower frequency values. Nevertheless, this cutoff frequency is shifted to higher values with increasing the superconductor layer thickness. Moreover, we found that the width and the number of the photonic bandgaps can be controlled by order of Fibonacci sequence. Our results are promising for the design of tunable filtering devices.

Compact High-Efficiency Broadband Metamaterial Polarizing Reflector at Microwave Frequencies

A compact highly efficient broadband microwave polarizing reflector, employing a quasi-2-D metamaterial composed of a single layer of square split-ring resonators, is presented and its performance is reported. Numerical and experimental results show a cross-polarization average polarization conversion ratio of greater than 90% for normal incident linearly polarized waves over a frequency range of 8.2–23 GHz. Due to multiple resonances occurring over this frequency range, the polarizing reflector presents both broadband performance and high polarization conversion efficiency. Transfer matrix and equivalent surface impedance theory and modeling are discussed to explain the physical underpinnings of the reflector’s multiresonance behavior. These physical mechanisms are further analyzed by examination of simulated surface current distributions. The reflector is expected to be employed in applications where the control of the signal polarization is of central importance.

A Method for Determining the Length of FBG Sensors Accurately

In this letter, we propose a method for estimating the length of single-mode fiber Bragg grating type sensors with high accuracy. Our method is based on calculating the maximum oscillation frequency of the side-lobes of the FBG reflection spectrum. We show that this frequency is independent of the stress field to which the sensor is subjected, and is dependent on the length of the sensor. This method can be used to characterize the gauge length of already installed FBG sensors so that they can provide useful data for engineering models of structural integrity. All the analyses are based on the approximated transfer matrix model, which is a newly developed numerical method for the analysis of the FBG reflection spectrum under various stress fields.

Semi-analytical modeling and optimization of a traveling wave sandwich piezoelectric transducer with a beam-ring combined structure

Abstract Boasting the advantages of low maximum ground pressure and low locomotion resistance of tracked mechanisms, a traveling wave sandwich piezoelectric transducer with a beam-ring combined structure was proposed and developed to directly drive a metal track, and preliminary experimental investigations have confirmed the feasibility of the transducer design and its operating principle. However, the dynamic behavior of the sandwich piezoelectric transducer has not yet been studied theoretically. To enable practical applications, the sandwich piezoelectric transducer needs to be optimized for better output performances. Therefore, a semi-analytical model is of significance to describe the dynamic behavior of the sandwich piezoelectric transducer, to predict its driving effect, and to improve its output performance. In this study, an electromechanical coupling model is developed for the sandwich piezoelectric transducer by employing the transfer matrix method, in which a novel longitudinal-bending coupling vibration transfer matrix is created for the combined PZT elements and an in-plane bending vibration transfer matrix is developed for the closed curved beam element. To validate the proposed model, experimental investigations are carried out to measure the dynamic behavior of the transducer prototype and compare to calculation results. The differences between the measured and calculated resonant frequencies for two operating vibration modes are, respectively, 74 Hz and 63 Hz. Also the vibration shapes at the respective resonant frequencies match well. Comparisons demonstrate the feasibility of the developed transfer matrix model. To improve the output performance of the transducer, model-based optimization is conducted. The optimized geometrical sizes are obtained to meet optimization goals of the transducer.

Tuning of the defect mode in a 1D superconductor-semiconductor crystal with hydrostatic pressure dependent frequency of the transverse optical phonons

This study aims to investigate a transmittance spectrum in a one-dimensional photonic crystal, which is surrounded by air and composed of alternating layers of a superconductor (HgBa2Ca2Cu3O8+δ) and a semiconductor (GaAs), using the transfer matrix and two-fluid models. Herein, we considered the pressure-dependence of the superconductor’s critical temperature and the pressure-dependence, in the semiconductor, in both the angular frequency of the transverse optical phonons and the thickness of layers. Initially, we found that increasing the pressure for fixed thickness values of the superconductor results in a shift in the larger frequencies of the transmittance spectrum and the photonic band gaps. With an increase in the thickness of the superconductor layer at a fixed pressure and thickness values of the semiconductor, an increase in the width of the photonic band gaps was observed. When a defective GaAs semiconductor layer was inserted into the structure due to the dissipative features of the semiconductor, a defective mode with a transmittance of less than 1.0 was found inside the photonic band gaps. When the thickness of the superconductor layer was increased, while keeping the pressure and thickness of the semiconductor constant, the defect mode shifted to shorter frequencies. It was also found that the shift and the number of defective modes in the photonic band gaps increase when the thickness of the defective semiconductor layer increases.